This invention relates to pressure-sensitive adhesive tapes, adhesive tabs formed therefrom, and methods for manufacturing the same. In one aspect, the invention relates to improvements in stretchable tapes and like products, and in the manufacture of the same. In this aspect, the stretchable tapes are formed of multiple layers that are manually stretchable to enable their stretchable properties. In another aspect, the invention relates to improvements in laminate web constructions of diaper fastener-tab stock of the kind adapted to be supplied to a diaper manufacturer and to be separated by the manufacturer into individual diaper-fastening tabs and applied to individual diapers, usually two tabs to a diaper for infant diapers and six tabs to a diaper for adult diapers. In this aspect, the invention particularly relates to means forming part of the diaper tabs and providing novel conveniently manipulated fingerlifts for the tabs.
The tapes are useful in a wide range of applications and constructions wherein a stretchable or variable length connector is required and/or a closing tension is to be applied to two elements as in a protective cover or item of personal clothing such as a gown. The tapes may be used as a construction film for forming an element of a more comprehensive tape or closure system including industrial or craft applications requiring pieces to be secured together with tension during a drying cycle or medical applications such as medical tapes, suture tapes, nasal dilators, bandages and the like. In such broad applications, the tape layers may be formed of polymeric, stretchable polymer and fabric constructions and cellulosic materials. The tapes are especially useful in connection with diaper fastening systems, and they are described hereinafter with particular reference to stretchable fastening tapes for use in diapers, diaper tabs and the manufacture of the foregoing.
The use of stretchable or extensible fastening tapes in diaper tabs to promote user comfort through better fit and more secure mounting is known in the art. The tabs operate as extensible diaper side waist bands. Examples of such diaper fastening systems are disclosed in U.S. Pat. Nos. 4,795,456, 4,066,081, 4,051,853 and 3,800,796. The teachings of these patents are incorporated herein by reference.
It has been previously proposed to make articles from pressure-sensitive adhesive tapes in which the layer of pressure-sensitive adhesive is partially covered with a printed pattern of ink or other non-printed masking agents such as talc. For example, document or envelope containers are shown in U.S. Pat. Nos. 3,159,930 and 3,874,893, labels are shown in U.S. Pat. No. 4,068,028, a tacky floor mat is taught in U.S. Pat. No. 4,107,811 and sign stock is described in U.S. Pat. Nos. 4,671,003 and 4,787,158.
Various fingerlift arrangements specific to diaper tabs are also known in the prior art. One simple arrangement is to provide an adhesive-free zone at the fingerlift edge, as in U.S. Pat. No. 3,833,456 to Reed et al. This fingerlift edge can be difficult to grasp;
there is no clear indication of the presence of a fingerlift, and the unsupported edges of rolls from which such tabs are cut can be easily damaged.
Another fingerlift arrangement for a diaper tab is a fold-over arrangement, as in U.S. Pat. No. 3,893,460 to Karami. If such folding-over is done during manufacture of the diaper fastener stock, differences in thickness are created across the width of the stock, causing distortions when the stock is rolled up for storage and shipment. On the other hand, if the folding-over is delayed only to be attempted on the diaper line, the difficulty of performing that step as part of the fastener dispensing and application procedure on the diaper line presents a risk of line stops and delays in diaper production.
Another known fingerlift arrangement for a diaper tab is a strip lamination, as in U.S. Pat. No. 4,726,971 to Pape et al. The laminated strip extends outwardly of the width of the diaper fastener stock, so that when the same is rolled and transported, the laminated strip can be easily damaged. Also, the strip creates local thickness variations in the roll.
Still another arrangement is a pull string, as in U.S. Pat. No. 4,005,713 to Mesek. This too may cause thickness variations, and may be complicated to fabricate and manipulate, particularly at high diaper line speeds.
The inventive stretchable tape has a multiple layer construction including an adhesive layer for tape mounting of normally nonextensible and extensible layers that selectively bear tension loads. An adhesive-inhibiting masking is applied to a portion of the adhesive layer to enable relative movement between the extensible layer and adjacent adhesive layer portion to thereby provide the tape with stretchable properties.
The stretchable tape includes opposed terminal segments and a central segment. The nonextensible layer typically comprises a facestock material or substrate extending along the length of the tape. The extensible layer and adhesive masking are located adjacent the central segment. A separation line or plane is provided at the central segment.
The separation line may comprise a location of fully separated portions of the facestock or nonextensible layer, such portions being respectively associated with opposed terminal segments, or a weakened joint in the facestock layer that may be ruptured by manual stretching of the tape. The weakened joint may be formed by a tape supplier, a tape converter or an ultimate tape user such as a diaper manufacturer. The weakened joint may be formed in the facestock layer by mechanical or chemical techniques. Mechanical techniques include forming discontinuities along a failure line as by scoring, perforating, slitting or any other means known in the art. Chemical techniques include acid drip or etching.
As it relates to a fastening tape or diaper tab herein, the facestock layer has tear strength or modulus characteristics that enable it to be manufactured and processed in customary web or film sizes using conventional automated machinery that impose insufficient forces to rupture, plastically stretch or otherwise detrimentally deform the layer. The separation lines extend in the machine direction and do not tend to interfere with machine direction forces applied to the stock to carry it through the processing.
For diaper applications, the length of the fastening tape is formed in the machine cross direction and transverse direction of the stock, so that the separation line extends across the width of the tape. If the separation line comprises complete partitioning of the facestock layer, the portions of the facestock layer may simply separate to allow tape stretchability. If the separation line is a weakened joint, the tape may be manually stretched to rupture the facestock layer along the joint, and thereby transfer stretching forces to the extensible layer and achieve stretchable tape or tab properties.
In another aspect, the adhesive masking may provide a distinctive color appearance as by phosphorescence or fluorescence. This distinctive color appearance may be provided for any number of applications including designation of location of control or manipulative elements.
In diaper applications, the high visibility of the fingerlift provided by the phosphorescence or fluorescence is useful in typical household infant diaper applications. It is especially useful in a health care facility when it is not desirable to fully light the room and disturb the patient whose diaper is to be checked or changed. Further, the distinctive appearance may serve as a warning to avoid contact. For example, the protective latex gloves worn by the attendant or nurse may be torn if the pressure-sensitive adhesive is inadvertently contacted and then pulled-free.
In contrast with the prior art use of adhesive barriers, in the present invention as it relates to tapes, the adhesive masking is provided along a continuous zone or line using web processing apparatus and techniques. In addition to enabling relative movement between adjacent layers as noted above, the continuous application of the adhesive masking may form end fingerlifts.
In one aspect, the present invention involves the concept of utilizing such means to eliminate or minimize complications, constraints and disadvantages involved in pattern-coating substrates with pressure-sensitive adhesive in the manufacture of tapes and other articles. In particular, the invention minimizes or eliminates complications, constraints and disadvantages involved in the need to pattern-coat the adhesive.
The adhesive masking is applied along continuous stripes or zones in a selected masking pattern corresponding with required areas of adhesive deadening to eliminate the need for pattern coating of the adhesive. The masking may be applied in a high speed web processing technique such as printing, roll-coating, extrusion or coextrusion.
The adhesive masking also enables the adhesive layer to be continuous at the separation line so that adjacent portions of the web material tend to remain in the plane of the web during processing. In contrast, pattern coated webs do not have adhesive adjacent the separation line. More particularly, xe2x80x9cgapsxe2x80x9d exist between spaced portions of the pattern coated adhesive as shown in U.S. Pat. No. 4,795,456, which patent is also owned by the assignee of this application. The overlying portions of the facestock layers at such gaps may tend to move out of the plane of the web or fold-over during processing so as to expose interior layers which may have a different coefficient of friction as compared with the surface of the web normally intended to be exposed.
Upon exposure of such an interior layer, it may interfere with uniform travel of the layers along roller surfaces or other friction supporting members due to its different coefficient of friction. This is particularly troublesome upon exposure of an interior extensible layer which tends to have a significantly higher coefficient of friction. In order to more closely match the coefficients of these surfaces, it is known in the art to emboss the surface of the extensible layer in order to reduce its coefficient of friction. The present invention eliminates the need for such an embossing step.
The invention enables the manufacture of fastening tape stock and diaper fastener or tab stock of substantially uniform thickness from one edge to the other, with attendant advantages to the manufacturer and converter. Also, a stripe of the masking agent may be applied to the outer most edges of the stock in order to provide adhesive-free and therefore xe2x80x9cpickxe2x80x9d-free roll edges.
The invention also enables stretchable tape to be formed with continuous line production techniques including applying adhesive inhibiting masking along selected continuous stripes of the adhesive surface using high-speed line processes such as printing, roll coating, extrusion and coextrusion. The adhesive masking may be a single layer construction or a multiple layer construction to provide function specific layers to enhance adhesion, cohesion, bonding or friction properties.
In accordance with the foregoing improvements, the invention provides for the manufacture of stretchable diaper fastener or tab stock, and stretchable diaper fastening tabs formed from such stock, in a manner compatible with current diaper manufacturing practice, providing improved diaper tabs, and improved tabbed diapers, at little or no increase in costs over the practices of the prior art.
In this respect, the present invention also provides diaper tab fasteners having fingerlifts (i.e., end tabs for the tab fasteners themselves) which are xe2x80x9cbuilt-in,xe2x80x9d which are easy and convenient to use, which overcome the problems of the prior art diaper tab fingerlifts including thickness variations and added material costs, and which offer new advantages including the ability to economically provide improved distinguishability of the fingerlifts from the remainder of the tabs, the ability to provide for the absorption of finger oils or other contaminants, and the ability to add fragrances to the tabs. The distinguishability may be further enhanced by use of adhesive masking having phosphorescence or fluorescence properties.
In a further aspect, the present convention relates to transfer tapes wherein the pressure sensitive adhesive layer is partially covered with a selected pattern of the adhesive masking. Once again, the adhesive masking is applied along continuous zones or stripes. The tape is formed in a whole or in part by slitting along the continuous stripe through the tape substrate, the adhesive coating and the adhesive masking. In this manner, the need to pattern coat the substrate with pressure sensitive adhesive in the manufacture of transfer tapes and other articles is eliminated.
Accordingly, the present invention overcomes the inability to slit rolls of pre-manufactured transfer tape stock to various widths on demand, and eliminates the corresponding need to manufacture and inventory various widths of transfer tape pending demand for one or the other specific width or widths. The invention enables the manufacture of tape stock and tapes with attendant advantages to the manufacturer and converter. The transfer tapes may be used in the manufacturer of the stretchable tapes, fastening tapes, tape stocks, diaper tabs and diaper tab stock in accordance with the invention.